The present invention relates to a method and apparatus for simultaneously coating and strengthening the inside surface of hollow pipe. It is understood that most of the pipe subjected to this method and apparatus would be concrete, clay or other similar aluminum silicate product used to carry water or sewage or the like. However, the process and even the apparatus could be adapted to plastic or metal conduit if the need arose.
Pipe, particularly conduit which is buried in the ground, made from a concrete or clay has a tendency to crack and leak from freezing and thawing as well as from pressure exerted on the exterior surface by trucks and machinery. Most of this type of pipe is buried beneath the surface of roadways or right of ways and is in sections that are joined together at customary intervals. Often the sections have a so called "man hole" at the points of intersection of the pipe sections so that access may be obtained to the interior of the pipe to service phone or electric lines, to deal with leaks of gas or just to service possible breaks or leaks.
Since replacement of underground pipe is expensive, not only due to cost of materials and labor but because the roadway must often be closed to traffic and torn up, it is desirable to be able to maintain such conduits usable for the longest possible time.
Impregnating the interior surfaces of such conduit against the flow of moisture or gases is of some help and has been tried in the past. A pipe liner is also a solution that has been tried. The liner forms a sort of pipe within a pipe and in some cases has been made from a material which deforms under heat and pressure such that an attempt can be made bond the liner to the interior conduit surface.
A part of the entire problem is that many of the conduits involved require apertures for the joining of "laterals" and other lines from smaller to larger pipes or mains as they are sometimes called.
Another problem that confronts the repair of such conduits or pipes is that many of them carry liquid and the liquid must be temporarily drained and re-routed. Also, leakage of surface water and the like into the conduit must be prevented by increasing the pressure within the conduit temporarily to a pressure greater than the exterior hydrostatic pressure around the pipe which causes the leaking in the first place.
It is impractical to attempt to hand seal each individual crack in the conduit and such crack does not make the pipeline or conduit stronger against the outside pressures against it which will result in further fissures and breaks. It is therefore most desirable to make the repairs and increase the tensile strength of the conduit at the same time if that can be accomplished.